maorae



Jan. 15,1929. 1,699,112

' D. M RAE v vAcuuu amen Apm IETHOD onus/mine UP RESIDUAL GASES THEIREIN Filed Jan. 192s IINVENTO'R Duncan/Yacfiae Ratented Jan, 15, 1929.

UNITED STATES PATENT orries,

Duncan anemia, or mar cannon, new JERSEY, Assmuon T0 wss'rmonousn LAMP COMPANY, A. CORPORATION OF vacuum isvrcs um mmnou or eLEAumG or mmm ussns msnsm.

4ppl1cstton nearanuar s, 1m. Serial in. 011,612.

This invention relates to vacuum devices and more articularly to evacuated electron devices an j the cleaning up of residual'gases therein. v n

An object of my invention is, to provide a method of cleaning up residual gascsin the bulbs of electron devices or the like, byforming the plate thereofof galvanized iron or other suitable material coated with zinc and vaporizing the zinc thereof, whereby the residual uses in the bulb are sufficiently eliminate/ Another object of m invention is the provision of an electron evice or the like with aclean-up agent thereon applied as an even coatin or deposit on' a component part thereo such as theplate, and adapted to be activated by heating the plate, in an deiiil'able manner.- after exhaustion o the A further olg'cct of my invention is the provisionof ra i0 tubes or the'like in which a cheaper material than the customary molybdenum, for exam le, 1 zinc-plated or galvanized iron, is used For the plates there,-

of, the zinc or the like serving the double,

' function of preventing rusting of the iron prior to its introduction into such devices and a cleaning up residual gases in the I 1 XllZGd iron or some other relatively inexpenbulb u :1 activation thereof. g I

A still further ob ect-of my invention s the production of radio bulbs suitable for detector tubes or the like inwhich the required. degree of exhaust is obtained ina simple and economical manner.

Other objects and advantages of the,in-

vention will be made apparent as the de scription proceeds. I w

"Various materials 1 have been used for cleaning up residual gases in evacuated elec' tron devices such as radio bulbs,'X-ray tubes and the like. In the copending application of H C. Rentschler, Serial No. 582,261 filed August 16, 1922, vacuumdevices and method of exhausting-the same, (W. L. 198) and assigned to the Westinghouse Lamp Com; pany,isdescribed a method ofcleamng up residual gases in electron tubes by activating'aluminum vor aluminum and magnesium or'the like" therein; The'said. application sets form how the useflof Isuch clean-up agents obviates the necessity of producing a ve high vacuum in the device by'mechan ice means, such as a vacuum pump. Such cleaning-up agents, therefore, make it possi- 5 ble to exhaust the device to a moderate degree only and, then produce the required 1gb vacuum by vaporizing or activating the particular cleanup agent used.

The clean-u agents mentioned in said copending QPPllCfliSlOl'l'll'e aluminmn,'magneslum, calcium and hosphorus, all of which have been used with varying degrees of success. All of such materials havcheretofore been ordinarily applied as stri )S or small pieces 1n a certain position on t 1e plates of radio bulbs, when used therein, and activated by heating such plates b high-frequency induction or electron boin ardment to temperatures suiiicient to vaporize the material 7 used. The disadvantage ofsuch an arrangement, is that a plate consisting of relatively expensive material, such as molybdenum, tungstenor the like, must ordinarily be employed and additional labor is involved in 7. attaching the clean-up material thereto, as by welding, pasting, clipping orfthe like.

According to my invention, I obviate-the necessity of using expcnsivc material, such as that mentioned, and avoul the additional 8 ofieration of fastening clean-up material t ereto, by forming the plate directly from a composite metallic sheet, such as galva- .ment of a plate uniformly covered or coated with a suitable clean-up agent and said plate may beof an desired material such as iron, nickel, moly )denum, tungsten or the 05 like." Likewise, theclean-up agent may be" any suitable material, such as zinc, aluminum, magnesium, calcium, an alloy or mixture oftwo or more ofthe same or the like applied to the plate as a uniform film or coating by electro-plating, galvanizing or any other desired process. My invention will better be understood by reference to'the accompanying drawing, the single figure of which is a side elevation, partly in section, ofa radio tube embed ing my invention and surrounded b a 001 for inductively heating the plate t ereof, and

did

bulb 2, a stem 3 sealed therein and a base 4.

Supported on the stem 3 is an electrode. or plate 5, another electrode or grid 6 and a cathode in the form of an electron-emit-' ting filament 7. The stem, together with the aforementioned suitably-supported electrodes, form the mount of the electron device 1. Lead-in wire 8 connects the plate 5 to a suitable contact member 9 on the base. Lead-in wire 11 extends between the grid 6' and contact member 12 on the base 4;.

The filament 7 is provided with leading-1n wires 13 and 14;, connected, respectively, to contactmembers 15 and 16 on the base 4. The plate 5 is preferably constructed of galvanized iron or iron electroplated with zinc, although it may consist of-molybdenum, nickel, tungsten or the like, to which zinc has been applied as a clean-up-agent, or any of the mentioned plate materials, uniformly coated with any suitable plean-up agent, such as zinc, aluminum, magnesium or calcium.

The grid 6 may be constructed of any suitable material, for example, one of the metals mentioned for-constructing the plate. The filament 7 may be formed as an oxidecoated, platinum-iridium wire or of activated, thoriated or pure tungsten wire, or any other material suitable for electronemission purposes. Prior to its introduction into the bulb, the plate 5, it of galvanized iron, is preferably cleaned'ot foreign material, such as dirt or grease, and, if of molyb-.

denum or one of the other metals mentioned, may have applied thereto a thin sheet or foil of zinc or, by electroplating or the like, uniformly coated with a. thin plating ofzinc, aluminum, magnesium, calcium or-an alloy or mixture of two or more of the same.

A combination of two or more of such clean-up agents may also be employed. The bulb 2 may then be cold-exhausted on an oil pump of the usual type to obtain a moderate vacuum therein, such as that ranging from 1 to 100 microns. The bulb 2 may then be tipped off and a coil 17, suitably connected to a high-frequency generator'18 or other suitable source of high-frequency current through a switch 19, may be applied therearound, as shown in the drawing.

Upon closing the switch 19, high-frequency current in the coil. 17, will induce corresponding current in the plate and also in the residual gases in the bulb 2. These induced currents will heat the plate and other conducting parts of the device and cause the residual gases to glow. or flash brightly, until the plate 5 becomes heated sufficiently to cause vaporizationor activation of the cleanup a ent 21 thereon. Let it be assumed that such clean-up agent, ac-

cording to 'the preferred. embodiment illustrated, is zinc in the form of galvanizing or electroplating .on an iron plate 5. An advantage obtalned by thls preferred arrangement is cheapness, as-it is well known that galvanized iron is much cheaper than molybdenum or other conventional plate materials.

The zinc on thesurface of the iron not only serves to prevent rusting of the same prior to its introduction into the electron device but it also protects the surface of the iron from occluding atmospheric gases and the like, for, as is well known, iron is galvanized by being dip ed into molten zinc. Such a process heats t e iron to a temperature suflicientto drive off a .large propor- ,tion of occluded gases and the film of the zinc, deposited on the surface thereof, substantially prevents occlusion of additional gas, after the galvanizing process has ban completed. Some of the advantages of my invention may however be secured by using iron electroplated with zinc, magnesium or the like, for, in that way, the iron is prevented from rusting prior to use, and the amount of the cleanup agent may be conveniently controlled by variation of the time or the plat ing current during the process of elctroplating. In its broader aspect, my invention also contemplates the use of zinc as a cleanup material or .a material or getter to improve the operation of an electron device and may be, applied in any manner; for ex ample, it may be applied as a cLp or'stri on the plate 5 in the same manner in-whic the aluminum clean-up agentlwas applied according to the copending application of Bentschler aforementioned. hen the temperature of. the plate 5 has risen sufliciently, the zinc or' other clean up agent thereon melts, vaporizes a'nd satis-' faetorily cleans-up the residual gases in the bulb, as well as those driven oil? from the plate. Any other suitable method of heating the plate 0 may be used instead-of the in-.

iio

ductive heating heretofore described, for example, the filament 7 may be heated to an. electron-emitting temperature by passing an a electric current therethrough, and the plate pressing a high potential between said heated filament and the plate. If zinc is used as'the cleanup material, a mirror of the ently does not remove the residual gases as completely as magnesium, but, the remaining gases do not seem to harm the electron- 5, heated by electron bombardment, by im- Ira:

, milliamperes and a range of from 6 to emission of the filament as much as those remaining after a magnesium clean u Aft-- i er seasoning for '3 /h'0urs at 7 '.7 v0 ts, the,

ve electron tubeswiththorium activated filaments and magnesium,

plate current for clean-up, gave, when tested, an average of 27. milliamperes, while for; the four zinc tubes tested, unde'r indenti'cal conditions, the

average was 41 milliamperes and the range from to 54 milliamperes. 1 The gridcurrent was less than .1 of a microampere in the magnesiumtubes and ranged" rom .3 to; fiiltmicroamperes in the zinc-tubes.

ii The fact that a; zinc clean-upv leaves some means of practicing .my invention, as applied to radio'tubes, it is to be understood that my invention is applicable to X-ray tubes or any other evacuteddevices add that thelconsti'uctionof the radio tubes and the proportion of the zinc or other clean-up agent -on the plate and the' method of applicatiog thereof may lie'varied within the spirit an scopeof my invention, as defined by the appended clalms.

-What is claimed is:

1; A vaccuum device comprising a bulb exhausted to a moderate degree and containin a galvanized iron electrode adapted to be eated to cause a vaporization of the zinc thereon to effect a clean-up action on the residual gases.

2. A vacuum device comprising an envelope evacuated to a'moderate degree and containing a thermionically active cathode containing thorium and a plate composed of.

galvanzed' iron to which is attached a small piece-of magnesium, said plate being adapted to be heated to vaporize the zinc and magnesium, at least in part, to efliciently remove residual gases in the bulb.

In testimony whereof, I have hereunto subscribed my name this 8th day of January, 1923.

' DUNCAN MAG-RAE. 

